1. Field of the Invention
Example embodiments relate generally to wireless communication, and more particularly to a method and apparatus for adaptively allocating available bandwidth for network users. The method may be particularly applied to hypertext transfer protocol (HTTP)-based video streaming where a lower variability in rate adjustments with smoother temporal evolution of streaming rates may improve a user's viewing experience while maximizing the number of supported users.
2. Related Art
As shown in FIG. 1, an inherent conventional characteristic of wireless networks is user heterogeneity in the sense that users 10 close to a base station 1 enjoy strong channels, while distant users 20 receive far weaker signals. To increase the QoE for all users 10/20, ideally a higher time-average rate would be applied to all users. However, due to a shortage of network resources, a more realistic alternative is to allow users to have heterogeneous channel conditions, and hence different resource requirements for a given bit rate.
Especially with regard to video traffic, this type of traffic is experiencing tremendous growth that is partially fueled by the proliferation of online video content and the steady expansion in transmission bandwidths. The amount of video traffic is forecast to double annually in the next several years, and is expected to account for the dominant share of wireline and wireless Internet traffic.
The huge growth in traffic volume goes hand in hand with a shift towards hypertext transfer protocol (HTTP)-based adaptive streaming mechanisms, which allow the video rate to be adjusted to the available network bandwidth. In view of these trends, it is critical to design video streaming mechanisms that use the available network resources efficiently and provide an adequate quality-of-experience (QoE) to the users. While a comprehensive video quality perception metric is hard to define, it is widely agreed that the QoE improves not only with a higher time-average rate, but also with a smoother temporal evolution. Typically a fundamental trade-off arises between these two criteria, because a higher time-average rate entails a more responsive scheme that makes more aggressive rate adjustments, compromising smoothness. Measurement experiments indicate that currently deployed schemes do not necessarily perform well in that regard, and may induce high variability and even oscillations as a result of interactions among several rate-adaptive users. This has triggered numerous proposals for enhancements, involving a variety of techniques, ranging from multipath solutions, network caching, traffic shaping and layered coding to improved bandwidth estimation at the client side in conjunction with dynamic rate selection at the server side.
The above challenges are particularly pertinent in wireless networks where the available bandwidth is not only relatively limited, but also inherently uncertain and time-varying due to fading and user mobility. On the other hand, resource allocation mechanisms in wireless cellular networks offer greater capabilities for controlling the user throughput, especially since the wireless link is commonly the bottleneck in the end-to-end path. In particular, scheduling algorithms at the base stations tend to provide support for specifying suitable target throughputs for the various users, and thus ensuring a smooth streaming rate. The proposed enhancements of HTTP-based adaptive streaming mechanisms mentioned above have exploited a wide range of approaches for mitigating the impact of variations in network bandwidth at the client and/or server, but have not leveraged the option to exercise direct control over the user throughput at a network element.